No tool detection system and tool holder

ABSTRACT

A &#34;NO TOOL,&#34; &#34;BROKEN TOOL&#34; OR &#34;IMPROPERLY SET TOOL&#34; DETECTION DEVICE FOR USE WITH TAPS, DRILLS, REAMERS, BORING TOOLS, COUNTER BORES AND MILLING CUTTERS WHICH INCLUDES A TOOL HOLDER AND A MOVABLE SHELL THEREON NORMALLY BIASED OUTWARDLY OF EACH OTHER, WITH A RADIOACTIVE ELEMENT ON THE HOLDER AND THE SHELL NORMALLY SPACED FROM THE RADIOACTIVE ELMENT, IN CONJUNCTION WITH A RADIATION DETECTION SYSTEM WHEREBY UPON COMPRESSIVE ENGAGEMENT OF THE TOOL WITH A WORK PIECE DUE TO ITS LONGITUDINAL FEED, THERE WILL BE A RELATIVE MOVEMENT OF THE TOOL HOLDER AND SHELL SUCH AS WILL POSITION SAID SHELL TO PROTECTIVELY ENCLOSE SAID RADIATION ELEMENT, SAID RELATIVE MOVEMENT BEING PREVENTED WHEN THERE IS &#34;NO TOOL,&#34; &#34;A BROKEN TOOL&#34; OR AN &#34;IMPROPERLY SET TOOL&#34;, AND THE METHOD OF PROVIDING SAID DETECTION SYSTEM.

United States Patent [72] Inventor Theodore M. Smith Detroit. Mich. [2!]Appl. No. 804.604 [22] Filed Mar. 5, 1969 [4S] Patented Jane 28, I971[54] NO TOOL DETECTION SYSTEM AND TOO HOLDER 7 Claims, 2 Drawing Figs.

[52] US. PL 408/ 408/6; 10/129, 90/11, 250/83, 25QLl 0 [S1] lat.

323!) 47/00, B23q 1 1/00 [50] Field of Search 77/52; 250/83, 106, I08;90/] l; l0/l28, I29

[56] IelerelcesCKed UNITED STATES PATENTS 3,381,550 5/1968 Smith 77/5Primary Examiner-Francis l-lusar Attorney-Cullen, Sloman and CantorABSTRACT: A no tool," broken tool" or improperly set tool" detectiondevice for use with taps, drills, reamers, boring tools, counter boresand milling cutters which includes a tool holder and a movable shellthereon normally biased outwardly of each other, with a radioactiveelement on the holder and the shell normally spaced from the radioactiveelement, in conjunction with a radiation detection system whereby uponcompressive engagement of the tool with a work piece due to itslongitudinal feed, there will be a relative movement of the tool holderand shell such as will position said shell to protectively enclose saidradiation element, said relative movement being prevented when there isno tool, a broken tool" or an improperly set tool; and the method ofproviding said detection system.

fgggzggg a 33 may/km PATENTED JUN28 I9?! F i i mvemoa HEQDQRE M. SMITH(gi /v A m M ATTORNEYS N TOOL DETECTION SYSTEM AND TOOL HOLDERBACKGROUND OF TH E INVENTION In applicant's earlier issued U.S. Pat. No.3,38l,550 dated May 7, 1968, entitled, Apparatus For A Tool FailureDetection System," there was provided a compensating type of tool holderincluding a pair of relatively moveable parts. In that construction, aradioactive element was mounted upon one of the relatively movableparts, and a shielding device normally covering the radioactive elementwas mounted upon the other part. A failure of contemplated function ofthe tool in the machine tool was adapted to cause a relative movementbetween the parts such as would uncover the radioactive element toactivate a radiation detection system for avoiding damage to aworkpiece, to give an audible or visible signal. It was designed toprevent damage to workpieces on a production line which might nototherwise be discovered until after a complete machining operation withconsequent loss and expense.

In accordance with the present invention, the same principle may beemployed in a device to detect the presence automatically of no tool," abroken tool" or an improperly set tool" for taps, drills, reamers,boring tools, counter bores and milling cutters and give aninstantaneous signal by which the machine tool or production line may beshut down until a proper tool is provided.

It is an object of the present invention to provide an im proved toolholder whereby upon the existence of either no tool," a broken tool" oran improperly set tool" after a predetermined feed movement of the toolholder and a shell such as would normally be caused by engagement of aproperly set tool with respect to the workpiece to activate a radiationdetection system and for automatically shutting down the equipment.

It is a further object to incorporate in the present system and inconjunction with such tool holder, an electrical'circuit which includesa radiation detection system whichcircuit is nonnally closed-andincorporating a limit switch or the like which ismechanically orelectrically opened upon such normal feed movement of the tool'holderwhich with a normal tool properly set would otherwise compressivelyengage the workpiece so that relative movement of the workpiece holderparts would cause a shielding of the radioactive element.

The detail of construction for the mounting and protectively enclosingof a radioactive ring upon a tool holder is set forth in applicant'scopending U.S. Pat. application, Ser. No. 489,522 filed Sept. 23, 1965.

It is another object to provide an improved tool holder which mounts aradioactive element in a very simple construction which includes a shellmounted over the tool holder and normally biased so as to expose theradioactive element and which upon'contact of a, tool within the toolholder with a workpiece with the tool properly set will cause suchrelative movement of the shell with respect to the tool holder as toprotectively enclose the radioactive element.

These and other objects will be. seen'from. thefollowing specificationand claims in conjunction with the appended drawing in which:

FIG. 1 is a longitudinal section of the present tool holder deteetiondevice withv the power and feed spindle and workpiece fragmentarilyshown.

FIG. 2 is a schematic diagram of the electrical circuit of the radiationdetection system.

DETAILED DESCRIPTION The cutting tool T is shown spaced from theworkpiece W, Y

fragmentarily shown, said tool holder being mounted within aconventional type work driving and feeding spindle S, the

arrow 12 indicating conventional type of reciprocal feed movement whichmay be employed and the numeral 13 designating the direction of rotationof said spindle.

Said spindle has a bore 14 and projected there into the radial key 15which registers with a corresponding key-way 16 within the shank 17 oftool holder 18.

Adjusting nut 19 is mounted over said shank and secured in desiredposition by set screw 20. 7

Secondary set screw 21 projects radially inward through said spindle andengages the tapered portion 22 of said shank as one means of effectivelylocking the tool holder shank within said spindle for rotative drive asdesired.

The tool holder adjacent one end has a bore 23 terminating in acounterbore 24 of slightly smaller diameter adapted to cooperativelyreceive the shank 25 of the cutting tool adapter Said adapter is of agenerally conventional construction includes the transverse lockingscrew 27 and the drive key 28 and is removably inserted within the toolholder with the shank 25 projected snugly into the bore 24 and looselyinto the bore 23 as shown in FIG. 1.

A series of transverse ball receiving bores 29 are formed through thewall of said holder and communicate with bore 23 and are adapted tomovably nest the shank retaining balls 30 whose inward adjustment foranchoring the shank is limited to the positioning shown in FIG. 1.

The shank has an annular locking groove 31 whose outer walls are taperedoutwardly and are in retained registry with the respective balls 30, ofwhich there are three in the illustra tive embodiment.

One of the tapered surfaces corresponding to said groove 31 is in thenature of a cam 32 adapted to disengage the balls from the recess 31 topermit withdrawal of the shank 25 and adapter 26 when the surroundingshell40 has been moved longitudinally so that its internal-annularrecess 43 is in registry with the balls as hereafter described. 4

The tool holder at the end of bore 23 has a counterbore 33 terminatingin an axial threaded aperture into which is projected the threaded-endof bolt 34. Said boltextends axially outwardwithin counterbore 33 andterminates in the enlarged head 35. Coiled compression spring 36surrounds bolt 34 and bears against a portion of the tool holder at-thebase of counterbore 33.

The other end of spring 36 bears against the inturned stop flange37 ofthe pressure pad 38 with the headed'portion of.

the bolt 34 extending up into the bore 39 of said pressure pad.

In the assembled position of the adapt'er'shank 25 within the toolholder, the inner end of said shankis compressively engaged by thepressure 'pad38'which is normally biased outwardly by the spring 36thereby placing tension at all times upon said shank; said coil springbeing in compression with the adapter inserted as shown in FIG. 1.

Mounted over and surrounding the outer portion of the tool holder is ashell'40 which has an annular groove 41 providing a grip to facilitateretraction of said shell manually.

Said shell includes the bore 42 which snugly and slidably receives toolholder 18 and formed within said bore is the annular counterbore or ringgroove 43 by: which with the shell The interior surfaced of the shellhas an elongated additional counterbore 44 which defines the shoulder 45at the forward end thereof as shown in the drawing.

The compression spring 46 is nested within the bore 44 and engages theshoulder 45 at one end and at its opposite end, engages the-washer 48anchored by the snap ring 47 mounted upon the tool holder.

The shell intermediate its ends has an internal shoulder correspondingto the inner end of the bore 44 by which upon engagement with the ring47 limits relative outward movement of said shell to the position shownin FIG. 1. A central portion of the tool holder normally outward of saidshell has an annular groove 49 within which is nested and fixedlysecured en-' closed radioactive ring 50.

In normal operation with a properly set tool T mounted by the adapter 26operative engagement of the tool with the workpiece W due to a feedmovement of the spindle S will cause a relative movement of the toolholder with respect to said shell so that the shell will nonnallyenclose protectively said radioactive ring 50 and prevent the escape oremission of radioactive rays such as would otherwise activate aradiation detection system.

The radioactive ring 50 is impregnated with a radioactive substance andin the normal position of the parts of the tool holder with the tool Tout of contact with the workpiece is exposed due to the relativepositioning of the shell 40.

The rays normally-emitted from the radioactive element or ring 50 areadapted to activate a radiation detector such as shown schematically inFIG. 2.

The present detection system 51 includes a detector D of the Geiger tubetype which is adapted to sense radioactive rays when emitted fromelement 50 on the tool holder under certain conditions.

In the circuit shown in FIG. 2, an electrical amplifier and indicatorcontrol 52 is biased by normally closed limit switch 60 to ground. v

The amplifier and indicator control assembly 52 is connected to detectorD by the lead wires 54, and also to power source 53.

The radiation detection system includes off and on" switch 58, resetbutton 59 and the lead 55 to the signal device 56 which may be a bulb orlight or an audiblesignal.

In the same circuit in series therewith there is schematically shown acontrol element 57, which when energized, may be adapted to either shutdown the machine tool or to effect a withdrawal with the tool holderspindle to an inoperative position.

The present Geiger tube type of detector senses the exposure of theradioactive element 50 whenever there is a failure of relativelongitudinal movement between the tool holder and the shell 40 which isshown in FIG. 1 and bears against tool holder adapter 26.

The increase in detector count rays causes the electronic circuitry todeflect a meter relay in the detection system generally indicated at 52which may include, as shown in FIG. 2 schematically, an amplifier and anindicator control in an electrical circuit which forms no part of thepresent invention, for activation of an alarm relay assembly in turn,energizing the alarm light 56 or other signal or the control mechanism57. This illustrates one circuit by which the present detection systemfunctions.

Electronic parts such as generally designated at 51- with the type ofcircuitry shown in FIG. 2 are sold by Eberline instrument Company andothers. The circuitry and construction of the detection system forms nopart of the present invention but merely illustrative of one suchdetection system with which the present tool holder may be adapted.

In the illustrative embodiment, the sealed source of radioactiveradiation material 50 should be such that one-fourth inch, forillustration, of the shell 40 will give an alternation of approximately1,000.

There is, thus, employed in connection with the radioactive element 50,beta radiation or low energy gamma radiation. Sources of these may be asfollows:

Strontium-90 Cerium-144 Krypton-I85 Thallium-204 Radium-D Radium-E Thisis by way of illustration only and not limitations, since it iscontemplated that other nuclides may be suitable for this purpose in thelow energy range.

The present tool holder device provides for the use of radioactiveisotopes in the form of the radioactive element or ring 50 applied to atool holder and wherein upon the existence of no tool, a broken tool" oran improperly set tool, the normal relative movement of the tool holderwith respect to the shell which would otherwise cause shielding of theradioactive element is prevented, with the result that the.

emitted rays from the radiating element are available to activate theradiation detection system 51, provided the same has been energized.

ln the present construction, as the tool holder is activated by thespindle S and before contact normally of the tool T with the workpieceW, the radioactive element 50 is unshielded, FIG. 1.

During this period, however, a circuit which includes the radiationdetector is open, noting the limit switch 60 which is normally closed.It is only after such longitudinal feed of the spindle S as wouldnormally place a properly set tool T in engagement with the workpiece W,that such feed movement causes the stop 61 as mounted upon the spindleand shown schematically in FIG. 2 to mechanically open limit switch 60;thus, activating the radiation detection circuit.

At that time, however, if the workpiece W has been properly engaged bythe tool T, there will be a compressive movement of the tool holder 18with respect to the shell 40 with the result that the tool holder andthe radioactive element 50 mounted thereon will move so as to beshielded by said shell. Such movement can be for a distance equal to thespace between the adapter 26 and the outer end of the holder shown inFIG. 1 at which time the radioactive element 50 would be completelyshielded by the shell.

Thus, under those conditions, the signal mechanism 56-57 would not beactivated. This is the normal situation.

On the other hand, if there is no tool present, as can happen, or abroken tool" or an improperly set tool, then the above mentioned inwardfeed movement of the spindle will not cause the above described relativemovement between the holder and the shell with the result that theradioactive element 50 will remain exposed and at the proper time,activate the detection system.

At the end of the boring or tapping operation, the tool holder 18 iswithdrawn by the spindle. Just as soon as the contact 61 moves away fromlimit switch 60, the electronic circuit to the radiation detectiondevice is closed or grounded and inhibits the detection system.

It is noted, furthermore, that with the presence of a proper tool T,properly set, inward feed movement of the spindle and the connected toolT with respect to the workpiece W will cause a compression of the coilsprings 46 and 36.

Accordingly, when the holder retracts and is withdrawn, so that the toolis out of contact with the workpiece W, the springs 46 and 36 functionin their expansion so as to cause a relative outward movement of theshell 40 with respect to the tool holder such that the said shell ismoved so as to no longer enclose the radioactive element as shown in FIG. 1.

At the same time, such withdrawal movement of the spindle has closed thelimit switch 60 so that the radiation detection system is inoperative.

The present improved tool holder is a simplified construction in that itincorporates essentially, only the movable shell 40 which may bemanually retracted using the grip 41, to permit disengagement of theballs 30 which are cammed outwardly by the cam surface 32 on the shank25; said balls being adapted to move into the annular groove 43, then inregistry with the manually retracted shell.

As soon as manual pressure is removed from said shell, shell will moverelatively to the tool holder to the position shown in FIG. 1, theadapter 26 and its shank having already been removed.

It follows conversely that the shank 25 may not be inserted within thetool holder until the shell has also been manually retracted again toprovide a place for the balls to go during insertion of said shank untilthe locking groove 31 of said shank is in registry with said balls.

Thus the compression spring 46 serves the additional purpose ofproviding-a control for the insertion and removal of the tool adapter 26and its shank.

It is seen, furthermore, that under normal operating conditions with thetool T engaging the workpiece, both of the springs 46 and 36 are undercompression and the tool holder 18 has beenmoved inwardly so that theshell enclosed the radioactive element.

The springs, therefore, serve the additional cocking function so that assoon as the spindle and tool are retracted at the end of a cuttingoperation, the parts will automatically reassume the position shown inFIG. 1. l 7

Having described my invention, reference should now be had to thefollowing claims.

Iclaim:

1. In a no tool," "broken tool," or improperly set tool detection devicefor taps, drills, reamers, boring tools, counter bores and millingcutters;

an elongated tool holder having a bore at one end and a shank at itsother end adapted for connection to a source of rotative power andlongitudinal reciprocal feed;

a radioactive impregnated element mounted upon said holder;

a cylindrical shell movably mounted over said holder;

spring means interposed in compression between said holder and shellnormally maintaining said shell spaced from and exposing saidradioactive element;

an adapter mounting a tool for operative engagement with a workpiece,and a shank on the adapter projected into the tool holder bore andinterlocked therewith;

said adapter engaging said shell and spaced from said holder;

means mounting the adapter shank for operative driven engagement withsaid holder and for longitudinal movement of the holder relative to saidshell on engagement of said tool with said workpiece;

said relative movement causing said shell to cover and enclose saidradioactive element;

the rays from said radioactive element adapted to energize a radiationdetection system upon failure of relative longitudinal movement due tothe existence of no tool, "a broken tool," or an improperly set tool";

- retraction of said longitudinal feed and disengagement of said tooland workpiece permitting relative movement of said tool holder and shellin the opposite direction for spacing the shell from said radioactiveelement.

2. In the detection device of claim 1, an electrical circuit includingsaid radiation detection system;

and a normally closed switch in the circuit mechanically opened uponsuch longitudinal feed movement of said tool holder as would bring aproperly set tool into contact with said workpiece.

3. In the detection device of claim 1, a pressure pad axially mountedadjacent and yieldably spaced from the inner end of said tool holderbore;

and spring means biasing said pad outwardly; said adapter shank onassembly into said bore operatively engaging saidpressure pad placingsaid adapter shank under tension, said pressure pad normally urging saidadapter shank outwardly of said tool holder.

4. In the detection device of claim 1, there being a plurality of spacedtransverse bores extending through said tool holder into its bore;

said adapter shank having an annular locking groove;

a ball in each of said transverse bores movably projecting tion and lowenergy gamma radiation.

6. In the detection device of claim 1, the radioactive element beingselected from the group consisting of Strontium- 90, Ceriuml44,Krypton-185, Thallim-204, Radium-D and Radium-E.

7. In the detection device of claim 1, said radioactive elements beingin the form of a ring mounted on said tool holder, said shell in thefonn of a sleeve upon said relative movement adapted to protectivelyenclose said ring.

